RESULTS OF CULTIVATION. 
269 
becoming well aired and oxygenized, as it is under high culture. 
Under the sod of a lawn, therefore, the roots of trees will be 
nearer the surface than in ground under cultivation, and will have 
less power to resist cold, so far as deep roots enable them to re¬ 
sist it. 
If a tree is planted in a thoroughly drained soil which is to be 
cultivated, instead of one which is to be covered with lawn, it may 
be set several inches deeper, so that the main roots need not be 
injured by the spade, while they will be kept in warm soil by the 
occasional turning under of the surface which has been under the 
direct action of the sun’s rays. The roots at the depth of ten 
inches, in a soil which is spaded annually, and well cultivated, will 
be as well aired, and have as warm feeding ground, as in a similar 
soil two inches below an old sod. This cultivation, therefore, gains 
for the tree a summer and winter mulching of eight inches in depth 
above its rootlets; a great gain in winter, and equal to several 
degrees of more southern latitude. 
Half-hardy trees should therefore not only be planted in ground 
drained most deeply and thoroughly, but also where the ground 
may be deeply cultivated until they are rooted in a warm subsoil 
below the action of frosts—say ten years. Trees which even¬ 
tually grow to considerable size may, when young, be centres or 
parts of groups of shrubs that also require high culture ; and when 
the tree begins to over-top the shrubs, the latter should be gradu¬ 
ally removed. But it must be constantly borne in mind that all 
trees, and especially those of doubtful hardiness, need a full de¬ 
velopment of low side-branches when young, and no shrubbery 
should remain near enough to them to check this side-growth. 
When all the excess of shrubbery around the tree is removed, and 
the latter is supposed to have become sufficiently established to be 
able to dispense with deep culture, and have the ground under its 
branches converted into lawn, then two or three inches in depth 
of fresh soil should be added all around the tree, as far as the 
roots extend ; and for half-hardy trees, an autumn mulching with 
leaves or evergreen boughs should never be omitted at any age 
of the tree. The subject of mulching will be treated again in this 
chapter. 
